South Korean authorities reported Tuesday that two patients infected with MERS, the Middle East Respiratory Syndrome, have died and the total number of infected with deadly virus has risen to 25. This is the largest MERS outbreak outside of the Middle East.

The first two deaths associated with the MERS outbreak in South Korea occurred Monday according to the Ministry of Health. The victims were a 58-year-old woman who died of acute respiratory failure and a 71-year-old man. Both tested positive for the virus before they died.

Also Tuesday, authorities disclosed that two of the new patients who came down with the virus are apparently the first in South Korea to become infected by so-called “third level exposures.”

Up until now, all of the infected patients in South Korea had direct contact with the first patient diagnosed with MERS in South Korea, making them “second level exposures.”

Known as patient number 1, he is a 68-year-old Korean man who contracted MERS in May after returning to Seoul from a trip to Bahrain, Saudi Arabia and the United Arab Emirates.

Kwon Jun-wook, director of South Korea’s MERS management team within the Ministry of Health and Welfare, said the two new cases have been traced back not to patient 1, but to patient 16.

Kwon said these two cases were found to have shared the same hospital room with the 16th patient.

But he also noted that so far the virus has been contained. The new cases of MERS diagnosed within the last 24 hours, Kwon said, have come from within the group of nearly 800 South Koreans who were already quarantined or isolated after being exposed to an infected person.

The MERS virus initially produces flu-like symptoms such as fever and coughing, though these can escalate to pneumonia and kidney failure. There is no known cure or vaccine for MERS.

The MERS virus was discovered in Saudi Arabia in 2012. The World Health Organization (WHO) says that camels in the Middle East are the likely primary source of the MERS virus that is infecting humans. It is unclear how the virus passes from the animals to humans. But between humans, coughing and direct contact with fluids from infected people can spread the virus.

Kim Woo-joo, a professor of infectious diseases at Korea University, who is working with the government to contain the MERs outbreak, said the public can take precautions to limit the spread of the disease.

Kim said wearing a mask, washing hands frequently and covering the mouth when coughing should be enough to prevent infection.

The MERS outbreak in South Korea is the largest outside of the Middle East. There is also one reported case in China. He is a Korean businessman who was reportedly exposed to patient 1 in Seoul, then travelled to China through Hong Kong before he was diagnosed with the disease.

The Ministry of Health’s Kwon Jun-wook said the South Korea government is now in the process of imposing a travel ban for anyone who has been exposed to the virus.

Kwon said a list of about 240 people under quarantine has already been sent to the Ministry of Justice, and the ministry strongly urged them to send a list of everyone under quarantine. He said they are working to comply with this request.

MERS is a deadly strain of the coronavirus family that also includes the common cold and SARS, the Severe Acute Respiratory Syndrome. During the SARS outbreak over a decade ago that centered around China and Hong Kong, over 8,000 people were infected and nearly 800 died.

According to the World Health Organization there have been over 1,000 MERS cases worldwide so far with at least 400 related deaths.